Retractable syringes have become increasingly important and desirable for use in hospitals and medical facilities for a number of reasons. In particular, retractable syringes are typically limited to a single use, where the hypodermic needle of the syringe is withdrawn into the syringe after aspiration and injection of a fluid, thus preventing multiple uses of the syringe and the potential transmission of human immunodeficiency virus (HIV) as well as other diseases from patient-to-patient. The retraction of the needle within the syringe after use also shields the needle and prevents inadvertent needle jabs or pricks from occurring to patients and health care providers.
A variety of different retractable syringe devices have been designed to effectively withdraw the needle within the syringe after a single use. However, the challenge exists to design a retractable syringe that is limited to a single use yet is simplistic in design and assembly, such that the syringe can be produced on a large production scale while minimizing manufacturing costs.
A number of single use retractable syringes are known in the art including, without limitation, devices described in U.S. Pat. Nos. 5,578,011, 5,632,733, 6,090,077, and 5,935,104, the disclosures of which are incorporated herein by reference in their entireties. Additional embodiments of retractable needle syringes are also described in co-pending U.S. patent application Ser. No. 11/249,741, the disclosure of which is incorporated herein by reference in its entirety.
In retractable syringes such as the types described above, the syringe needle is typically withdrawn or retracted into a cavity within the plunger of the syringe after a single use. A resilient biasing member, such as a coil spring, is typically utilized to force the needle into the plunger after use. It would be beneficial to enhance operation of the syringe by controlling the force and velocity at which the needle is retracted within the plunger cavity as well as ensure the needle does not inadvertently escape from the plunger cavity once it has retracted within the plunger.